1. Field of the Invention
The present invention relates generally to a method of efficiently processing a dormant state in a packet service between communication networks providing the packet service using different mobile communication techniques and a multi-mode terminal for the same.
2. Description of the Related Art
Recently, mobile communication networks are being upgraded from second generation (2G) networks, such as code division multiple access (CDMA) networks and Europe global systems for mobile communication (GSM) networks, to third generation (3G) networks such as wideband CDMA (WCDMA) networks. To efficiently and conveniently use 3G networks, the 3G networks should be installed to cover as wide an area as possible (e.g., nation wide). However, since 2G networks are widely installed and used at the present, it is difficult to remove the 2G networks at the same time. Thus, while infrastructures of the 2G networks are transitionally used, areas in which the 3G networks are installed are gradually widened usually from portions of metropolitan areas.
In this state, since it is economical in terms of service to mix a 2G CDMA scheme and a 3G WCDMA scheme, terminals supporting WCDMA are manufactured as multi-mode terminals for supporting CDMA and WCDMA. Distinguishable characteristics of these multi-mode terminals typically include an idle handover function for changing to a CDMA mode or a WCDMA mode, a traffic handover function for seamlessly changing to the CDMA mode when a multi-mode terminal moves to a WCDMA shadow area while talking, and a packet call reconnection function for reconnecting a packet type data call by changing to the CDMA mode or the WCDMA mode. Although the method of mixing the CDMA scheme and the 3G WCDMA scheme is convenient and economical because existing 2G CDMA networks may be used if necessary, since the multi-mode terminals must quickly change a mode and perform a handover and reconnection, hardware and software of the multi-mode terminal is usually more complicated than that of a single-mode terminal.
Mobile communication providers desire to introduce techniques for increasing utilization of a wireless network and decreasing an access costs. Despite a cellular provider's best efforts to reduce costs, conventional access techniques may still be prohibitively expensive. For example, if a packet service is used for a relatively long time, a service charge for the packet service may become problematic because of service/access charges. To solve this problem, a technique of maintaining a terminal in a dormant state while real data transmission or reception is not performed has been developed.
Dormant indicates a technique of maintaining an idle state when data transmission or reception is not performed between a Web browser of a terminal and a server and returning to an access state when a user demand is input. For a packet call, a state in which an application using the packet call is operating but not transmitting or receiving data to or from a wireless network is called a dormant or preservation state.
Typically, when a component managing a radio link of a terminal or a system uses a timer and determines that no data is transmitted to or received from a wireless network for a predetermined time, a dormant state is activated. If the dormant state is activated, a mobile communication provider releases the radio link to save wireless resources and stores only an Internet protocol (IP) address required to receive a packet call service and quality of service (QoS) indicating a grade of service of a user. After the timer is reset, if no data is transmitted to or received from the wireless network for a predetermined time, an operating application is terminated, and the stored IP address and QoS information are deleted.
FIG. 1 is a conceptual diagram of areas in which conventional CDMA and WCDMA network systems are installed. Referring to FIG. 1, if a multi-mode terminal 50 moves to a CDMA exclusive area 10 while operating in a WCDMA mode in a WCDMA network area (e.g., areas 20, 30, and/or 40), i.e., an overlay area, since the multi-mode terminal 50 cannot connect to any WCDMA base transceiver station (BTS), the multi-mode terminal 50 searches for a CDMA BTS, and if a CDMA BTS is found, the multi-mode terminal 50 changes from the WCDMA mode to a CDMA mode and terminates a handover. On the contrary, if the multi-mode terminal 50 moves to the overlay area, the multi-mode terminal 50 operating in the CDMA mode performs a handover to change to the WCDMA mode according to a predetermined condition. Even if a GSM network is used instead of a WCDMA network, the same procedures as described above are performed.
However, since the multi-mode terminal 50 cannot communicate with any BTS when moving to a shadow area or a boundary area in a dormant state, it is difficult for the multi-mode terminal 50 to return to a reconnection state (i.e., a previous state) even if the multi-mode terminal 50 attempts a reconnection.
A process of processing a dormant state in the WCDMA mode will now be described with reference to FIG. 2. In response to a packet service request from a user, a data application, i.e., a controller 120 transmits and receives data using a packet type path set through steps 200 to 220. If data transmission or reception is no longer performed, for example, after data communication is finished, a WCDMA BTS 100 activates a timer to determine whether the WCDMA BTS 100 begins a dormant state. If data transmission or reception is not performed until the timer expires, the WCDMA BTS 100 releases a radio link by transmitting a Radio Resource Control (RRC) CONNECTION RELEASE message to a WCDMA modem 110 in step 230. If the WCDMA modem 110 receives the RRC CONNECTION RELEASE message, the WCDMA modem 110 determines that the dormant state has begun and transmits a DORMANT INDICATION message to the controller 120 in step 235.
However, a terminal maintains IP address and QoS information obtained through ACTIVATE Packet Data Protocol (PDP) CONTEXT procedures of steps 210 and 215 and does not terminate a relevant application. Thereafter, the WCDMA BTS 100 activates a dormant timer, and if no data communication is performed with the WCDMA modem 110 until the dormant timer expires, the WCDMA BTS 100 deletes the IP address and QoS information allocated to the terminal through DEACTIVATE PDP CONTEXT procedures of steps 240 to 245. In step 250, the WCDMA modem 110 transmits a CALL DISCONNECT message to the controller 120 to terminate the relevant application in use.
As described above, even though the terminal moves to a shadow or boundary area in the dormant state, the WCDMA BTS 100 cannot process a service from a WCDMA network, such as an incoming call or a short message, until the dormant timer expires.
A process of processing a dormant state in the CDMA mode will now be described with reference to FIG. 3. Similar to the WCDMA mode, in the CDMA mode, if a wireless data transmission or reception is finished and/or no longer performed after a packet bearer is established in step 320. the CDMA BTS 140 activates a timer to determine whether the CDMA BTS 140 begins a dormant state. For example, when a user accesses a certain site using the terminal, if the user does not act further until the timer expires in order to obtain more information after data communication for displaying a screen image is finished, a connection between the terminal and the CDMA BTS 140 is temporarily terminated. If no data is transmitted or received through a CDMA modem 130, the CDMA BTS 140 releases a radio link by transmitting a RELEASE ORDER message to the CDMA modem 130 in step 325. Steps 300-320 include conventional origination techniques and are not discussed here for the sake of clarity.
If the CDMA modem 130 receives the RELEASE ORDER message in step 325, the CDMA modem 130 determines that the dormant state begins from the moment the message is received and transmits a DORMANT INDICATION message for indicating the dormant state to the controller 120 in step 330. However, the terminal maintains previously obtained IP address and QoS information and does not terminate a relevant application. Thereafter, the CDMA modem 130 activates a dormant timer, and if no data communication is performed with the CDMA BTS 140 until the dormant timer expires, the CDMA modem 130 deletes the allocated IP address and QoS information and transmits a CALL DISCONNECT message to the controller 120 in step 335 to terminate the relevant application in use.
As described above, in the dormant state, even though a terminal moves to a shadow or boundary area, when a dormant timer expires, after terminating a relevant application and returning to a stand-by state, the terminal tries a mode change by determining whether a current area is the shadow or boundary area. Thus, in the dormant state, the terminal must wait without processing a message received from a network until the dormant timer expires. In addition, in the CDMA mode, the terminal determines whether a mode change is performed by periodically checking a WCDMA overlay bit included in a system parameter message. However, in the dormant state, even though a condition for a mode change is satisfied, the terminal must maintain the CDMA mode without changing to the WCDMA mode until the dormant timer expires.